This invention relates to a disk cartridge such as a magnetic disk cartridge, an optical disk cartridge or magneto-optical disk cartridge, and, more particularly, to a disk cartridge whose upper case and lower case are ultrasonically welded to each other.
FIG. 9 is a bottom view of an upper case with a cleaning sheet attached thereto in a conventional magnetic disk cartridge. FIG. 10 is a top plan view of a lower case with the cleaning sheet attached thereto in the magnetic disk cartridge. FIG. 11 is an enlarged cross-sectional view illustrating a state where the upper and lower cases of the magnetic disk cartridge are subjected to ultrasonic welding. FIG. 12 is an enlarged cross-sectional view of a resilient member disposed in the magnetic disk cartridge.
The magnetic disk cartridge mainly comprises a cartridge case 1, a magnetic disk 2 (see FIG. 12) accommodated rotatably therein, and a shutter (not shown) supported slidably by the cartridge case 1 and adapted to open and close head insertion ports or apertures 5.
The cartridge case 1 comprises an upper case 1a and a lower case 1b which are formed of a hard synthetic resin, such as an ABS resin. As shown in FIG. 10, an opening 4 in which a rotating and driving shaft is inserted is formed substantially in the center of the lower case 1b, and the head insertion port 5 having a rectangular shape is provided in the vicinity thereof. The upper case 1a is similarly provided with the head insertion port 5 (see FIG. 9).
A plurality of protrusions 3 arranged in parallel at predetermined positions and arcuate restricting ribs 6 for restricting the accommodation position of the magnetic disk 2 are provided on an inner surface of the upper case 1a. A cleaning sheet 7 made of, for instance, a non-woven fabric formed of a mixture of rayon fibers and polyester fibers, is placed in the space surrounded by the restraining ribs 6. Since the cleaning sheet 7 is thus placed, the protrusions 3 are covered with the cleaning sheet 7, and the peripheral portion of the cleaning sheet 7 is heat-bonded to the upper case 1a at a portion 9 by means of ultrasonic welding or a similar method.
As shown in FIGS. 10 and 12, a protruding support 10 and adhesion preventing protrusions 11 are provided on the inner surface of the lower case 1b and at a position substantially opposing the protrusions 3 of the upper case 1a. In addition, a proximal end portion 13 of a resilient member 12 formed by bending a plastic sheet into the form of a chevron is secured to the inner surface of the lower case 1b in the vicinity of the support 10 by a suitable means, such as bonding or welding. The distal end portion of the resilient member 12 is provided with an inclined portion 14 which projects in such a manner as to be inclined relative to the lower case 1b.
The lower case 1b is also provided with the restricting ribs 6 in the same way as the upper case 1a, and the cleaning sheet 7 is placed on the inner side thereof. Since the cleaning sheet 7 is thus placed, the resilient member 12 is covered, and most of the peripheral portion of the cleaning sheet 7 is welded or heat-bonded to the lower case 1b at the portion 9. However, a portion of the peripheral portion of the cleaning sheet 7 opposed to the opposite side ends of the resilient member 12 is not heat-bonded.
As shown in FIG. 9, bosses 15 are provided in the vicinity of the four corners of the upper case 1a, and, as shown in FIG. 10, cylindrical portions 16 into which the bosses 15 are inserted are provided in the vicinity of the four corners of the lower case 1b, respectively. As shown in FIG. 11, a portion 17 of allowance for welding is formed at the tip portion of each of the bosses 15, and the bosses 15 are respectively inserted into the cylindrical portions 16 with the portions 17 of allowance for fusion facing downward. Subsequently, as ultrasonic energy is supplied to the contacting portions of the boss 15 and the cylindrical portion 16, the portions of allowance 17 for fusion are melted, and the tip portions of the bosses 15 are thereby bonded to the inner bottom surfaces of the cylindrical portions 16.
If the disk cartridge is assembled by thus bonding together the upper case 1a and the lower case 1b as a unit, the cleaning sheet 7 on the side of the lower case 1b is partially lifted by the inclined portion 14 of the resilient member 12, as shown in FIG. 12, while a part of the cleaning sheet 7 in the upper case 1a opposed to the lifted portion is slightly pushed downwardly by the protrusions 3 provided on the upper case 1a. Consequently, the magnetic disk 2 is clamped lightly and resiliently by the upper and lower cleaning sheets 7. Then, as the magnetic disk 2 rotates, the surfaces of the disk are cleaned by the cleaning sheets 7.
In cases where the resilient member 12 and the cleaning sheets 7 are used to clean the magnetic disk 2, the portion of the cleaning sheet 7 lifted most highly by the resilient member (inclined portion 14), i.e., point C in FIG. 12, has the largest cleaning effect, and this point C (which is a straight line in a plane parallel to the disk 2) is referred to as the cleaning position in this specification or description.
As shown in FIG. 10, in a conventional disk cartridge, the aforementioned resilient member 12 and the like are disposed in such a manner that this cleaning point C is located in the range of from 90 to 120 degrees upstream of a center line X of the head insertion port 5 in the rotating direction of the disk.
In the conventional disk cartridge, when the boss portion 15 is, as shown in FIG. 11, inserted into the cylindrical portion 16, and the two members are welded by ultrasonic energy, an air flow including resin particles is generated by vibrations. The air is, as designated by an arrow in FIG. 11, introduced into the cartridge case 1 via an opening of the cylindrical portion 16. As a result, parts of the resin particles are allowed to adhere to the surface of the magnetic disk 2, causing errors at the time of recording and/or reproduction.
An object of the present invention is to provide a disk cartridge which can overcome the above-described problem and which has an enhanced reliability without the occurrence of errors due to adhesion of the resin particles to the surface of the magnetic disk.